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Volume 1 Issue 11, November 2016

Duration matters

Measuring the relevance of different dimensions of electricity provision is complex, especially in rural environments and developing countries, but it provides important information to define access policy priorities. Aklin et al. survey 8,568 households in rural India and find that an increase in the number of hours of electricity per day provides greater satisfaction to end users than reliability or stability.

Comment

Combining silicon and other materials in tandem solar cells is one approach to enhancing the overall power conversion efficiency of the cells. We argue that top cell partners for silicon tandem solar cells should be selected on the basis of their spectral efficiency — their efficiency resolved by wavelength.

News & Views

Energy access entails a range of metrics that need to be monitored to guide planning and implementation of electricity provision in developing nations. A study based on an extensive household survey carried out in rural India demonstrates that electricity supply duration is the best predictor for satisfaction with electricity service.

Concentrated thermoelectric generators convert solar energy to electricity, but historically their conversion efficiency has lagged behind their potential. Now, full system efficiencies of 7.4% are achieved by segmentation of two thermoelectric materials and a spectrally selective surface.

The degradation and failure of Li-ion batteries is strongly associated with electrode microstructure change upon (de)lithiation. Now, an operando X-ray tomography approach is shown to correlate changes in the microstructure of electrodes to cell performance, and thereby predict degradation pathways.

Nanostructured metallic crystals are already used to catalyse energy conversions, such as those that occur in fuel cells. However, to design improved materials, a deeper understanding of nanocrystal growth is required. Now, details of the mechanisms underpinning the synthesis of highly active, bimetallic Pt–Ni electrocatalysts are elucidated.

Richard D. Tilley

& J. Justin Gooding

Perspective & Review

Perovskite solar cells have emerged as a potential low-cost alternative to existing technologies. In this Perspective, Park et al. explore a strategy for the commercialisation of perovskite solar cells.

Understanding of defect physics in perovskite-halide semiconductors is essential to control the effects of structural and chemical defects on the performance of perovskite solar cells. Petrozza and Ball review the current knowledge of defects in these materials.

Research

The performance of inverted perovskite solar cells has so far lagged behind that of their normal-structure counterparts. Wu et al. fabricate an inverted perovskite–fullerene solar cell with a graded heterojunction that achieves a certified efficiency of over 18% for a cell area of 1 cm2.

Defects affect the performance of photovoltaic devices, but their exact role is still under scrutiny. Luria et al. use 3D imaging of current pathways in a working CdTe solar cell with nanoscale resolution and observe electrically active defects, which contribute to conduction.

More efficient, noble metal-free catalysts are sought to generate hydrogen from aqueous solutions using light. Liu et al. achieve high quantum efficiencies using a system where the co-catalyst is proposed to consist of small NiSx particles that are not anchored to the Cd0.5Zn0.5S photocatalyst.

Solar thermoelectric generators are a promising technology for converting solar energy into electricity, however their efficiency has been limited to 5.2%. Kraemer et al. report a solar thermoelectric generator with an efficiency of 9.6%, resulting in 7.4% efficiency in a concentrating solar thermoelectric system.

Electricity is a fundamental aspect of socio-economic development. Urpelainen et al. survey 8,568 households in rural India and find that the average hours of available electricity is an important factor in household satisfaction with supply, whereas reliability and voltage stability are less important.